Electrochromism is a phenomenon displayed by some materials of reversibly changing optical properties by using bursts of charges to cause electrochemical redox (reduction and oxidation) reactions in electrochromic materials. The optical properties may include transmittance, reflectance, absorptance and emittance. In particular, electrochromic materials exhibit a reversible color changes. The optical state of an electrochromic material depends on the amount of charge injected or extracted. The optical state of an electrochromic film may refer to lightness, transparency, color, reflectance, etc. The electrochromic film's optical state could be set at any state by controlling the amount of charges. In an application of smart windows, electrochromic films are integrated with the glass window to become serviceable. Electric controller are used to control the electrochromic films integrated with glass windows (i.e., smart windows).
In this disclosure, we propose different methods for changing optical states of electrochromic materials.